JP2012191250A - Image processing device, image processing method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing device, an image processing method, and program which make it possible to heighten picture quality when scaling is applied to compression encoded image signals.SOLUTION: There is provided an image processing device comprising a noise detection unit which detects block noise based on a compression encoded input image signal and outputs noise information indicating the detected block noise; a scaling unit which applies scaling to the input image signal for enlarging or reducing the image indicated by the input image signal and outputs scaling information indicating an enlargement or a reduction ratio; an adjustment signal generation unit which outputs, on the basis of the noise information and scaling information, an adjustment signal indicating the degree of correction; and a correction unit which corrects, on the basis of the adjustment signal, the image signal to which scaling has been applied.

Description

  The present invention relates to an image processing device, an image processing method, and a program.

  For example, when an image is compressed using an encoding method using Discrete Cosine Transform (DCT) or the like, block distortion (hereinafter referred to as “block noise”) may occur. Under such circumstances, a technique for improving the image quality by correcting the image signal by reducing the block noise has been developed. As a technique for improving the image quality by correcting the image signal by reducing the block noise, for example, a technique described in Patent Document 1 can be cited.

JP-A-10-229546

  For example, a conventional technique for improving the image quality as described in Patent Document 1 (hereinafter sometimes simply referred to as “conventional technique”) is an image showing an image compression-coded using, for example, discrete cosine transform. Block noise of a signal (hereinafter, sometimes referred to as “compressed and encoded image signal”) is reduced, and image processing such as edge enhancement processing is performed on the image signal with reduced block noise. Therefore, since noise reduction processing for reducing block noise and image processing for improving image quality are performed, there is a possibility that high image quality can be achieved by using conventional techniques.

  Here, for example, when the scaling process for enlarging or reducing the image indicated by the image signal is performed after performing the noise reduction process and before performing the image process, the position where the block noise exists changes. There is a high possibility of doing. In the conventional technique, since the change of the position of the block noise due to the scaling process is not taken into consideration, the reduced block noise may be emphasized as a result of performing the image process such as the edge enhancement process. Therefore, even if the conventional technique is used, it is not always possible to achieve high image quality.

  The present invention has been made in view of the above problems, and an object of the present invention is to improve the image quality when scaling processing is performed on a compression-coded image signal. It is another object of the present invention to provide a new and improved image processing apparatus, image processing method, and program.

  In order to achieve the above object, according to a first aspect of the present invention, noise detection is performed to detect block noise based on a compression-coded input image signal and output noise information indicating the detected block noise. A scaling unit that performs enlargement or reduction of the image indicated by the input image signal, and outputs scaling information indicating the enlargement ratio or reduction ratio, and the noise information and the input image signal. An image processing unit comprising: an adjustment signal generating unit that outputs an adjustment signal indicating a degree of correction based on scaling information; and a correction unit that corrects the image signal subjected to the scaling process based on the adjustment signal. An apparatus is provided.

  With this configuration, it is possible to achieve high image quality when scaling processing is performed on a compression-encoded image signal.

  Further, the adjustment signal generation unit includes a noise measurement unit that specifies a distance from a block boundary of block noise in the enlarged or reduced image based on the noise information and the scaling information, and the specified block boundary And an adjustment signal output unit that outputs the adjustment signal corresponding to the distance from the device.

  Further, the noise measurement unit may specify a distance from the block boundary in the horizontal direction and / or a distance from the block boundary in the vertical direction.

  The adjustment signal generation unit may further include an adjustment unit that adjusts the degree of correction indicated by the adjustment signal based on information indicating the intensity of the block noise included in the noise information.

  The correction unit determines local block noise based on the image signal on which the scaling processing has been performed, adjusts the degree of correction indicated by the adjustment signal according to the determination result, and the degree of correction is The image signal on which the scaling processing has been performed may be corrected based on the adjusted adjustment signal.

  The adjustment signal generation unit may output an adjustment signal for adjusting the gain of the image signal, and the correction unit may adjust the gain of the image signal on which the scaling processing has been performed based on the adjustment signal. .

  Further, the image processing apparatus may further include a noise reduction unit that reduces block noise of the input image signal, and the scaling unit may perform the scaling process on the input image signal with reduced block noise.

  In order to achieve the above object, according to a second aspect of the present invention, block noise is detected based on a compression-coded input image signal, and noise information indicating the detected block noise is output. Performing a scaling process for enlarging or reducing the image indicated by the input image signal on the input image signal, outputting scaling information indicating the enlargement ratio or the reduction ratio, the noise information, and the scaling There is provided an image processing method comprising: outputting an adjustment signal indicating a degree of correction based on the information; and correcting the image signal on which the scaling processing has been performed based on the adjustment signal. .

  By using such a method, it is possible to improve the image quality when scaling processing is performed on a compression-coded image signal.

  In order to achieve the above object, according to a third aspect of the present invention, block noise is detected based on a compression-coded input image signal, and noise information indicating the detected block noise is output. Performing a scaling process for enlarging or reducing the image indicated by the input image signal on the input image signal, and outputting scaling information indicating an enlargement ratio or a reduction ratio, the noise information and the scaling information, A program for causing a computer to execute an adjustment signal indicating the degree of correction and a step of correcting the image signal subjected to the scaling process based on the adjustment signal is provided.

  By using such a program, it is possible to achieve high image quality when scaling processing is performed on a compression-encoded image signal.

  According to the present invention, it is possible to achieve high image quality when scaling processing is performed on a compression-coded image signal.

It is a block diagram which shows an example of a structure of the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows an example of the detection method of the block noise intensity | strength in the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows an example of the detection method of the block noise intensity | strength in the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows an example of the detection method of the block noise intensity | strength in the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows the 1st structural example of the adjustment signal production | generation part in the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing for demonstrating an example of the production | generation method of the adjustment signal in the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows the 2nd structural example of the adjustment signal production | generation part in the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing for demonstrating an example of the local correction process in the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing for demonstrating an example of the local correction process in the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing for demonstrating an example of the local correction process in the image processing apparatus which concerns on embodiment of this invention. It is explanatory drawing for demonstrating an example of the local correction process in the image processing apparatus which concerns on embodiment of this invention.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

In the following, description will be given in the following order.
1. 1. Image processing method according to an embodiment of the present invention 2. Image processing apparatus according to an embodiment of the present invention Program according to the embodiment of the present invention

(Image processing method according to an embodiment of the present invention)
Before describing the configuration of an image processing apparatus according to an embodiment of the present invention (hereinafter sometimes referred to as “image processing apparatus 100”), an overview of an image processing method according to an embodiment of the present invention will be described. In the following description, it is assumed that the image processing apparatus 100 performs processing related to the image processing method according to the embodiment of the present invention.

  As described above, after the noise reduction process and before the image process, the scaling process for enlarging or reducing the image (still image or moving image; the same applies hereinafter) indicated by the image signal is performed. In this case, there is a high possibility that the position where the block noise was present will change. Therefore, the image processing apparatus 100 according to the embodiment of the present invention shows block noise detected based on a compression-coded image signal to be processed (hereinafter sometimes referred to as “input image signal”). An adjustment signal indicating the degree of correction is generated based on the noise information and the scaling information indicating the enlargement ratio or reduction ratio in the scaling process. Then, the image processing apparatus 100 corrects an image signal that has been subjected to scaling processing on the input image signal (hereinafter, may be referred to as “scaling image signal”) based on the adjustment signal.

  Here, as the input image signal according to the embodiment of the present invention, for example, the image processing apparatus 100 receives a broadcast wave transmitted from a television tower or the like (directly or indirectly via a set top box or the like). However, the input image signal according to the embodiment of the present invention is not limited to the above. For example, the image processing apparatus 100 can process an image signal transmitted from an external apparatus via a network (or directly) as an input image signal. In addition, the image processing apparatus 100 converts, for example, an image signal obtained by decoding image data stored in a storage unit (described later) or an external recording medium removable from the image processing apparatus 100 into an input image signal. You may process as. Examples of the input image signal according to the embodiment of the present invention include MPEG-4 (ISO / IEC 14496), MPEG-2 (ISO / IEC 13818), MPEG-1, H.264, and the like. 261, H.H. 263, H.M. For example, an image signal encoded by an encoding method in which compression encoding is performed in units of blocks including a plurality of pixels, such as H.264. In the following, an example in which the input image signal according to the embodiment of the present invention is an image signal encoded in block units of 8 × 8 pixels, that is, the number of pixels in block units is “8”. Will be described.

  Moreover, examples of the noise information according to the embodiment of the present invention include information indicating the position of the block boundary and information indicating the block noise intensity (information indicating the strength of the block noise). More specifically, the image processing apparatus 100, for example, data indicating the start position of a block in an image (hereinafter, sometimes referred to as “b_pos”) and data indicating a block size (hereinafter, “b_size”). Is the information indicating the position of the block boundary. Here, as b_pos, for example, coordinate data indicating the coordinates of a pixel when a predetermined position (for example, the lower left of the image) of the image is used as the origin is cited. Further, as b_size, for example, data indicating the number of pixels in block units can be given. The image processing apparatus 100 can determine the block size using, for example, a block boundary position detection method described later. The image processing apparatus 100 can specify b_pos and b_size corresponding to each block based on the encoding method of the input image signal. Further, the image processing apparatus 100 uses, for example, data indicating the intensity of block noise (hereinafter, may be referred to as “b_str”) as information indicating the block noise intensity. A block noise intensity detection method according to an embodiment of the present invention will be described later.

  Further, examples of the adjustment signal according to the embodiment of the present invention include a signal (mask gain signal) for adjusting the gain of the image signal. Note that the adjustment signal according to the embodiment of the present invention is not limited to a signal for adjusting the gain of the image signal. For example, as the adjustment signal according to the embodiment of the present invention, a signal (for example, an image in the correction unit) that defines the degree of arbitrary image processing related to the correction of the image signal in the correction unit (described later) included in the image processing apparatus 100 is used. Signal that defines the level of processing corresponding to the processing). Hereinafter, the case where the image processing apparatus 100 according to the embodiment of the present invention generates an adjustment signal for adjusting the gain of an image signal will be mainly described as an example.

  The image processing apparatus 100 according to the embodiment of the present invention generates an adjustment signal based on noise information and scaling information as described above, and corrects the scaled image signal based on the adjustment signal. Therefore, in the image processing apparatus 100, for example, even if linear scaling or nonlinear scaling (for example, panorama wide or overscan) is performed on the input image signal, block noise is generated by image processing (correction processing). There is no emphasis. That is, the image processing apparatus 100 can realize more natural image processing even for an image in which block noise has occurred.

  Therefore, the image processing apparatus 100 can achieve high image quality when scaling processing is performed on a compression-encoded image signal.

  Hereinafter, an example of the configuration of the image processing apparatus 100 according to the embodiment of the present invention will be described, and a specific example of processing according to the image processing method according to the embodiment of the present invention will also be described.

(Image processing apparatus according to an embodiment of the present invention)
FIG. 1 is a block diagram illustrating an example of a configuration of an image processing apparatus 100 according to an embodiment of the present invention.

  The image processing apparatus 100 includes, for example, a noise detection unit 102, a noise reduction unit 104, a scaling unit 106, an adjustment signal generation unit 108, and a correction unit 110.

  The image processing apparatus 100 includes, for example, a control unit (not shown), a ROM (Read Only Memory; not shown), a RAM (Random Access Memory; not shown), a storage unit (not shown), and a decoder. An operation unit (not shown) that can be operated by the user, a display unit (not shown) for displaying various screens on the display screen, a communication unit (not shown) for communicating with an external device, and the like. May be. The image processing apparatus 100 connects the above-described constituent elements by, for example, a bus as a data transmission path.

  Here, the control unit (not shown) is configured by, for example, an MPU (Micro Processing Unit), various processing circuits, and the like, and controls the entire image processing apparatus 100. The control unit (not shown) may serve as, for example, a decoder, a noise detection unit 102, a noise reduction unit 104, a scaling unit 106, an adjustment signal generation unit 108, and a correction unit 110, which will be described later. Further, the control unit (not shown) encodes the image signal that has been subjected to the image processing by the correction unit 110 and records the image signal in the storage unit (not shown), for example. It may also serve to perform a process for.

  A ROM (not shown) stores control data such as programs and operation parameters used by a control unit (not shown). A RAM (not shown) temporarily stores programs executed by a control unit (not shown).

  The storage unit (not shown) is a storage unit included in the image processing apparatus 100, and stores various data such as image data and applications. Here, as the storage unit (not shown), for example, a magnetic recording medium such as a hard disk, a nonvolatile memory such as an EEPROM (Electrically Erasable and Programmable Read Only Memory), a flash memory (flash memory), or the like. nonvolatile memory).

  Examples of the operation unit (not shown) include a button, a direction key, a rotary selector such as a jog dial, or a combination thereof. The image processing apparatus 100 can also be connected to, for example, an operation input device (for example, a keyboard or a mouse) as an external apparatus of the image processing apparatus 100.

  Examples of the display unit (not shown) include a liquid crystal display (LCD) and an organic EL display (also referred to as an organic light emitting diode display). The display unit (not shown) may be a device capable of display and user operation, such as a touch screen.

  A communication unit (not shown) is a communication unit included in the image processing apparatus 100, and performs wireless / wired communication with an external apparatus via a network (or directly). Here, as a communication unit (not shown), for example, a communication antenna and an RF (Radio Frequency) circuit (wireless communication), an IEEE 802.15.1 port and a transmission / reception circuit (wireless communication), an IEEE 802.11b port and a transmission / reception A circuit (wireless communication) or a LAN (Local Area Network) terminal and a transmission / reception circuit (wired communication) can be used. In addition, as a network according to the embodiment of the present invention, for example, a wired network such as a LAN or a WAN (Wide Area Network), a wireless network such as a wireless WAN (WWAN; Wireless Wide Area Network) via a base station, or Examples include the Internet using a communication protocol such as TCP / IP (Transmission Control Protocol / Internet Protocol).

  Hereinafter, an example of processing (processing according to an image processing method) in the image processing apparatus 100 will be described while describing a configuration example of the image processing apparatus 100 according to the embodiment of the present invention illustrated in FIG.

  The noise detection unit 102 detects block noise based on the input image signal, and outputs noise information indicating the detected block noise. Here, examples of the noise information include information (b_pos, b_size) indicating the position of the block boundary and information (b_str) indicating the block noise intensity. Moreover, although the noise detection part 102 outputs the noise information corresponding to all the blocks irrespective of whether the block noise was detected, the process in the noise detection part 102 is not restricted above. For example, the noise detection unit 102 can selectively output noise information corresponding to a block determined to have detected block noise. For example, the noise detection unit 102 determines that no block noise has been detected when the value of the block step characteristic (work (x)) calculated by the block noise intensity detection method described later is 0 or less. judge.

[Example of block boundary position detection method]
Here, an example of a block boundary position detection method in the image processing apparatus 100 according to the embodiment of the present invention will be described. Hereinafter, a case where the image processing apparatus 100 determines the position of the block boundary in the horizontal direction in the image indicated by the input image signal will be described as an example. Note that the image processing apparatus 100 can also detect the position of the block boundary in the vertical direction in the image indicated by the input image signal by using the same method.

  The image processing apparatus 100 detects the position of the block boundary, for example, by integrating the difference signals between adjacent pixels in the horizontal direction in the input image signal within the screen.

  More specifically, for example, the image processing apparatus 100 calculates a difference absolute value (| D (x) −D (x + 1) |) of a pixel value D (for example, a luminance value) in adjacent pixels in the horizontal direction. In addition, the image processing apparatus 100 accumulates the calculated difference absolute values in the vertical direction, and calculates a cumulative value for each position in the horizontal direction. Here, the image processing apparatus 100 may calculate a histogram having the cumulative value as the frequency and the horizontal position as the class. Further, the image processing apparatus 100 uses a cumulative value for each calculated horizontal position and a predetermined threshold for determining the block position, and a horizontal position that is equal to or greater than the threshold (or greater than the threshold). Horizontal position) is determined. Here, examples of the threshold include a preset fixed value, but may be a variable value that can be adjusted. Then, the image processing apparatus 100 determines the determined position (for example, corresponding to the peak position in the histogram) as the block start position (block boundary position), and determines the distance between the determined positions as the block size. judge.

  The image processing apparatus 100 detects the position of the block boundary by using, for example, the method described above. Needless to say, the method of detecting the position of the block boundary in the image processing apparatus 100 according to the embodiment of the present invention is not limited to the above.

[Example of block noise intensity detection method]
Next, an example of a block noise intensity detection method in the image processing apparatus 100 according to the embodiment of the present invention will be described. 2, 3, and 4 are explanatory diagrams illustrating an example of a block noise intensity detection method in the image processing apparatus 100 according to the embodiment of the present invention. In the following, an example of a block noise intensity detection method will be described, taking as an example the case where the image processing apparatus 100 detects the intensity of horizontal block noise in an image indicated by an input image signal. Note that the image processing apparatus 100 can also detect the block noise intensity in the vertical direction in the image indicated by the input image signal by using the same method.

  For example, the image processing apparatus 100 calculates an absolute difference value based on a pixel value D (for example, a luminance value) at the target pixel x and a pixel value D at a pixel near the target pixel x. In the example illustrated in FIG. 2, the image processing apparatus 100 calculates the absolute difference values a to e using, for example, the following formulas 1 to 5. Note that the image processing apparatus 100 detects the block noise intensity for the target pixel x, for example, when there is no pixel in the vicinity of the target pixel x (or there are not enough pixels for detection). It is not necessary to perform the process concerning.

  When the absolute difference values a to e are calculated, the image processing apparatus 100 calculates a value (work (x)) indicating the step difference feature of the block corresponding to the target pixel x, for example, by the following mathematical formula 6. Here, Expression 6 is an operation for comparing the level difference c corresponding to the position of the target pixel x with the average value of the peripheral level differences.

work (x) = c- (a + b + d + e) / 4
... (Formula 6)

  For example, when the value of work (x) is 0 (zero) or less, the image processing apparatus 100 determines that block noise has not been detected, and when the value of work (x) is greater than 0 (zero). It is determined that block noise has been detected.

The image processing apparatus 100 calculates a value cnt_all (| V |) obtained by summing up work (x) in the entire image for each level and a value cnt_bb (| V |) obtained by summing up work (x) in the coordinates of the block boundary for each level. Calculate for each level (FIG. 3). The image processing apparatus 100 calculates “cnt_bb (| V |) / cnt_all (| V |)” for each level, and the calculated “cnt_bb (| V |) / cnt_all (| V |)” is predetermined. The maximum level exceeding the threshold th_bnd is detected as the block noise intensity.

(FIG. 4).

  Here, the image processing apparatus 100 sets b_str as a value indicating a level corresponding to the detected block noise (for example, a number for identifying the level), but the processing in the image processing apparatus 100 is not limited to the above. . For example, the image processing apparatus 100 can set b_str as a value associated with a number for identifying a level. Further, examples of the predetermined threshold th_bnd include a predetermined value, but the predetermined threshold th_bnd is not limited to the above. For example, the predetermined threshold th_bnd may be a value set by a user of the image processing apparatus 100 (hereinafter, simply referred to as “user”).

  The image processing apparatus 100 detects the block noise intensity, for example, by performing the processing as described above. Needless to say, the block noise intensity detection method in the image processing apparatus 100 according to the embodiment of the present invention is not limited to the above.

  With reference to FIG. 1 again, a configuration example of the image processing apparatus 100 according to the embodiment of the present invention will be described. The noise detection unit 102 outputs noise information, for example, by performing processing related to the detection method as described above. In addition, the noise detection unit 102 transmits the input image signal to the noise reduction unit 104. Note that the configuration of the image processing apparatus 100 according to the embodiment of the present invention is not limited to the configuration in which the noise detection unit 102 transmits the input image signal to the noise reduction unit 104. For example, the image processing apparatus 100 may input the input image signal to the noise reduction unit 104 without using the noise detection unit 102.

  The noise detection unit 102 can be realized by, for example, a dedicated processing circuit having an arbitrary configuration for performing the processing related to the detection method as described above, but the configuration of the noise detection unit 102 is not limited to the above. . For example, in the image processing apparatus 100 according to the embodiment of the present invention, a control unit (not shown) may serve as the noise detection unit 102, and the noise detection unit 102 is a general-purpose process that can perform other processes. It may be a circuit.

  The noise reduction unit 104 includes, for example, a filter circuit, and reduces block noise that can be included in the input image signal. In addition, the noise reduction unit 104 transmits the input image signal with reduced block noise to the scaling unit 106.

  Here, for example, the noise reduction unit 104 performs processing regardless of the block noise detection result in the noise detection unit 102, but the processing in the noise reduction unit 104 is not limited to the above. For example, the noise reduction unit 104 may selectively reduce block noise based on noise information transmitted from the noise detection unit 102. In the above case, the noise reduction unit 104 includes, for example, a configuration in which an input image signal is selectively input to a circuit related to noise reduction such as a filter circuit based on noise information, or a circuit related to noise reduction based on noise information. It is configured to selectively activate.

  The scaling unit 106 performs a scaling process for enlarging or reducing the image indicated by the input image signal on the transmitted input image signal. Then, the scaling unit 106 transmits the scaling information to the adjustment signal generation unit 108 and transmits the scaled image signal to the correction unit 110.

  Here, examples of the scaling process in the scaling unit 106 include a process for performing linear scaling and a process for performing nonlinear scaling (for example, panorama wide and overscan). The scaling unit 106 can be realized by a dedicated processing circuit having an arbitrary configuration for performing the scaling process as described above, but the configuration of the scaling unit 106 is not limited to the above. For example, in the image processing apparatus 100 according to the embodiment of the present invention, a control unit (not shown) may serve as the scaling unit 106, and the scaling unit 106 is a general-purpose processing circuit that can perform other processes. There may be.

  The adjustment signal generation unit 108 generates an adjustment signal based on the noise information transmitted from the noise detection unit 102 and the scaling information transmitted from the scaling unit 106. Then, the adjustment signal generation unit 108 transmits the generated adjustment signal to the correction unit 110.

  Note that the process in the adjustment signal generation unit 108 is not limited to the process of generating the adjustment signal based on the noise information transmitted from the noise detection unit 102. For example, the decoder can specify the position and intensity of block noise during the decoding process. Therefore, the adjustment signal generation unit 108, for example, when noise information indicating the position and intensity of block noise specified by a decoder included in the image processing apparatus 100 or an external decoder of the image processing apparatus 100 is transmitted. Processing may be performed using noise information transmitted from the decoder instead of noise information transmitted from the noise detection unit 102. Hereinafter, more specific processing of the adjustment signal generation unit 108 will be described by taking as an example the case where the adjustment signal generation unit 108 generates an adjustment signal using noise information transmitted from the noise detection unit 102.

[Configuration Example of Adjustment Signal Generation Unit 108]
(1) First Configuration Example FIG. 5 is an explanatory diagram illustrating a first configuration example of the adjustment signal generation unit 108 in the image processing apparatus 100 according to the embodiment of the present invention.

  The adjustment signal generation unit 108 according to the first configuration example includes, for example, a noise measurement unit 112, a filter unit 114, a minimum value determination unit 116, and an adjustment signal output unit 118.

  Based on the noise information and the scaling information, the noise measurement unit 112 specifies the distance from the block boundary of the block noise (hereinafter, may be referred to as “b_dist”) in the image enlarged or reduced by the scaling process. To do. Here, in FIG. 5, the noise measurement unit 112 includes a first noise measurement unit 112 </ b> A that specifies the distance from the horizontal block boundary, and a second noise measurement unit 112 </ b> B that specifies the distance from the vertical block boundary. The structure provided with is shown.

  Note that the noise measurement unit 112 according to the embodiment of the present invention is not limited to the configuration that specifies both the distance from the horizontal block boundary and the distance from the vertical block boundary. For example, the noise measurement unit 112 according to the embodiment of the present invention specifies either the distance from the horizontal block boundary or the distance from the vertical block boundary corresponding to the processing in the correction unit 110. It may be configured to.

[An example of how to identify the distance from the block boundary]
Here, an example of a method for specifying the distance from the block boundary in the image processing apparatus 100 according to the embodiment of the present invention will be described. Hereinafter, an example in which the image processing apparatus 100 specifies the distance from the block boundary will be described by taking the case where the distance from the block boundary in the horizontal direction is specified as an example. Note that the image processing apparatus 100 can also specify the distance from the block boundary in the vertical direction by using a similar method.

  The image processing apparatus 100 calculates b_dist by performing, for example, the following Expressions 7 and 8 using information (b_pos, b_size) indicating the position of the block boundary included in the noise information. Here, Equations 7 and 8 show an example of a b_dist calculation method when the number of pixels in block units is “8”. Further, “mod (d, X)” shown in Expression 7 is a remainder of X modulo d, and “rate” is an enlargement rate or reduction rate indicated by the scaling information. Equation 8 is an operation for converting a distance (0 to 7) corresponding to the number of pixels “8” as a block unit into a distance (0 to 3) corresponding to an example of processing in the adjustment signal output unit 118 described later. Is shown.

  The image processing apparatus 100 specifies the distance from the block boundary, for example, by performing the above processing. It goes without saying that the method for specifying the distance from the block boundary in the image processing apparatus 100 according to the embodiment of the present invention is not limited to the above.

  The noise measurement unit 112 performs, for example, the above processing in each of the first noise measurement unit 112A and the second noise measurement unit 112B. Then, the first noise measurement unit 112A outputs b_dist_H indicating the distance from the specified horizontal block boundary, and the second noise measurement unit 112B displays b_dist_V indicating the distance from the specified vertical block boundary. Is output. Here, examples of b_dist_H and b_dist_V include 2-bit digital data, but b_dist_H and b_dist_V are not limited to the above.

  In addition, the noise measurement unit 112 can be realized by, for example, a dedicated processing circuit having an arbitrary configuration for performing processing related to the above-described specific method, but the configuration of the noise measurement unit 112 is not limited to the above. I can't. For example, in the image processing apparatus 100 according to the embodiment of the present invention, a control unit (not shown) may serve as the noise measurement unit 112, and the noise measurement unit 112 is a general-purpose process that can perform other processes. It may be a circuit.

  The filter unit 114 is configured by a filter circuit such as a low-pass filter, for example, and filters b_dist transmitted from the noise measurement unit 112.

  Here, FIG. 5 shows a configuration in which the filter unit 114 includes a first filter unit 114A corresponding to the first noise measurement unit 112A and a second filter unit 114B corresponding to the second noise measurement unit 112B. However, the configuration of the filter unit 114 according to the embodiment of the present invention is not limited to the above. For example, when the noise measurement unit 112 is configured to specify either the distance from the horizontal block boundary or the distance from the vertical block boundary, the filter unit 114 may be connected to the noise measurement unit 112. Either one of the corresponding first filter unit 114A or second filter unit 114B may be configured.

  Further, the adjustment signal generation unit 108 may be configured not to include the filter unit 114, for example.

  The minimum value determination unit 116 includes, for example, a comparison circuit, determines the minimum value of b_dist_H and b_dist_V in the corresponding block, and transmits the minimum value to the adjustment signal output unit 118. For example, when the noise measurement unit 112 is configured to identify either the distance from the horizontal block boundary or the distance from the vertical block boundary, the adjustment signal generation unit 108 The value determination unit 116 may not be provided.

  The adjustment signal output unit 118 generates and outputs adjustment signals corresponding to the transmitted b_dist_H, b_dist_V, and the minimum value.

  FIG. 6 is an explanatory diagram for explaining an example of a method for generating an adjustment signal in the image processing apparatus 100 according to the embodiment of the present invention. Here, FIG. 6 illustrates an example of a gain curve used by the adjustment signal generation unit 108 (adjustment signal output unit 118) for generating the adjustment signal when the image processing apparatus 100 outputs an adjustment signal for adjusting the gain of the image signal. Is shown.

  The image processing apparatus 100 uses, for example, data indicating a gain curve as shown in FIG. 6 or a look-up table in which b_dist and gain adjustment amount are associated one-to-one, for example, for each process in the correction unit 110 or scaling. Each type of scaling processing performed in the unit 106 is stored in a storage unit (not shown), a ROM, or the like. For example, when the correction unit 110 performs frequency separation type edge enhancement processing, the image processing apparatus 100 may store a gain curve or a lookup table for each frequency band. In the above case, the image processing apparatus 100 can correct an image based on the frequency characteristics of noise of the input image signal, for example, by weakening the contour enhancement processing in a low frequency range or a high frequency range.

  The adjustment signal output unit 118 generates an adjustment signal corresponding to the transmitted b_dist_H, b_dist_V, and the minimum value by using the gain curve or the like, for example, for each process in the correction unit 110 or for each frequency band. Then, the adjustment signal output unit 118 outputs the generated adjustment signal.

  As described above, the image processing apparatus 100 according to the embodiment of the present invention is not limited to the adjustment signal for adjusting the gain of the image signal. For example, the image processing apparatus 100 generates an adjustment signal indicating the degree of image processing other than the gain adjustment. It is also possible to do. When generating an adjustment signal indicating the degree of image processing, the image processing apparatus 100 uses, for example, a lookup table in which the b_dist and the value indicating the degree of image processing are associated one-to-one with the correction unit 110. Each process, each frequency band, and each type of scaling process performed in the scaling unit 106 are stored in a storage unit (not shown), a ROM, or the like. Then, as in the case of generating the adjustment signal for adjusting the gain of the image signal, the image processing apparatus 100 uses the lookup table or the like to transmit the adjustment signals corresponding to b_dist_H, b_dist_V, and the minimum value, for example, And generated for each process in the correction unit 110 and for each frequency band.

  The adjustment signal generation unit 108 according to the first configuration example can generate an adjustment signal based on noise information and scaling information, for example, with the configuration shown in FIG. Note that the configuration of the adjustment signal generation unit 108 according to the embodiment of the present invention is not limited to the configuration illustrated in FIG.

(2) Second Configuration Example FIG. 7 is an explanatory diagram illustrating a second configuration example of the adjustment signal generation unit 108 in the image processing apparatus 100 according to the embodiment of the present invention.

  The adjustment signal generation unit 108 according to the second configuration example illustrated in FIG. 7 has basically the same configuration as the adjustment signal generation unit 108 according to the first configuration example illustrated in FIG. Compared with the adjustment signal generation unit 108 according to the first configuration example, the adjustment signal generation unit 108 according to the second configuration example further includes an adjustment unit 120.

  The adjustment unit 120 adjusts the degree of correction indicated by the adjustment signal based on information (b_str) indicating the strength of the block noise included in the noise information. More specifically, for example, when the value of b_str (value indicating the strength of block noise) is larger than a predetermined threshold, the adjustment unit 120 adjusts the adjustment signal so that the degree of correction becomes larger. To do. For example, the adjustment unit 120 may adjust the adjustment signal so that the degree of correction decreases as the value of b_str decreases.

  The adjustment signal generation unit 108 according to the second configuration example has basically the same configuration as the adjustment signal generation unit 108 according to the first configuration example shown in FIG. Therefore, the adjustment signal generation unit 108 according to the second configuration example uses the configuration shown in FIG. 7 to convert noise information and scaling information into the same manner as the adjustment signal generation unit 108 according to the first configuration example shown in FIG. Based on this, an adjustment signal can be generated.

  Further, the adjustment signal generation unit 108 according to the second configuration example further includes an adjustment unit 120 to adjust the degree of correction indicated by the adjustment signal based on the strength of the block noise detected by the noise detection unit 102. To do. Therefore, based on the adjustment signal output from the adjustment signal generation unit 108 according to the second configuration example, the image signal is corrected in the correction unit 110, so that the detection result in the noise detection unit 102 is reflected more. It is possible to correct the image signal.

  The image processing apparatus 100 includes an adjustment signal generation unit 108 having the configuration illustrated in FIGS. 5 and 7, for example. Note that the configuration of the adjustment signal generation unit 108 according to the embodiment of the present invention is not limited to the configurations illustrated in FIGS. 5 and 7. For example, although described below as an example of processing in the correction unit 110, the adjustment signal generation unit 108 further adjusts the adjustment signal based on a function for evaluating the block distortion strength for each block boundary, and the adjusted adjustment It is also possible to output a signal. In the above case, the image processing apparatus 100 can perform finer correction.

  With reference to FIG. 1 again, a configuration example of the image processing apparatus 100 according to the embodiment of the present invention will be described. The correction unit 110 corrects the scaled image signal transmitted from the scaling processing unit 106 based on the adjustment signal transmitted from the adjustment signal generation unit 108. For example, when the transmitted adjustment signal is an adjustment signal for adjusting the gain of the image signal, the correction unit 110 adjusts the gain of the scaled image signal using a multiplier or the like. When the transmitted adjustment signal is an adjustment signal indicating the degree of image processing other than gain adjustment, the correction unit 110 sets the processing level indicated by the adjustment signal (for example, the level related to the strength of processing). In response, image processing is performed.

  The correction unit 110 can prevent the block noise from being emphasized by correcting the scaled image signal based on the adjustment signal generated based on the noise information and the scaling information as described above, for example.

  Note that the processing in the correction unit 110 is not limited to the above. For example, the correction unit 110 can determine local block noise based on the scaled image signal and adjust the degree of correction indicated by the adjustment signal transmitted according to the determination result. Here, as the local block noise, for example, block noise generated at a block boundary can be cited. Then, the correction unit 110 corrects the scaling image signal based on the adjusted adjustment signal. In the above case, the image processing apparatus 100 can perform finer correction.

[Example of local correction processing]
8A to 8C and FIG. 9 are explanatory diagrams for explaining an example of local correction processing in the image processing apparatus 100 according to the embodiment of the present invention. Here, FIGS. 8A to 8B are explanatory diagrams for explaining an example of a method for determining local block noise generated at a block boundary in the image processing apparatus 100. FIG. 9 is an explanatory diagram illustrating an example of adjustment signal adjustment according to a local block noise determination result in the image processing apparatus 100. Hereinafter, an example in which the adjustment signal transmitted from the adjustment signal generation unit 108 is an adjustment signal for adjusting the gain of the image signal will be described as an example of local correction processing in the correction unit 110.

For example, the correction unit 110 performs the calculation of Equation 6 for the pixel at the block boundary (target pixel x) in the scaled image signal. Then, the correction unit 110 blocks based on bb_range (corresponding to work (x) shown in Equation 6), the threshold th _tex, and the threshold th _edge (th _tex <th _edge ), which is the calculation result in Equation 6. Determine block noise at the boundary. _{Here, th tex} is a threshold for determining the texture, for example, in the case bb_range of the following _{th tex (or,} less _{th tex.} Hereinafter the same.), The correction unit 110 corresponding to the pixel of interest The difference absolute value c is regarded as a texture. Further, th _edge is a threshold value for determining an edge. For example, when bb_range is greater than or equal to th _edge (or greater than th _edge ; the same shall apply hereinafter), the correction unit 110 corresponds to the target pixel. The difference absolute value c is regarded as an edge. Examples of the threshold th _tex for determining texture and the threshold th edge for determining _edge include predetermined values, but the threshold th _tex and the threshold th _edge are not limited to the above. For example, the threshold th _tex and the threshold th _edge may be values set by the user.

More specifically, for example, as illustrated in FIG. 8A, the correction unit 110 has a step (difference absolute value c) at the block boundary larger than steps (difference absolute values a, b, d, e) around the block. That is, for example, when th _tex ≦ bb_range <th _edge , it is determined as block noise. Further, for example, when the step at the block boundary is not larger than the step at the periphery of the block as shown in FIG. 8B, for example, when bb_range <th _tex , the correction unit 110 determines that the block noise is regarded as texture. do not do. Further, for example, when the step at the block boundary is sufficiently larger than the step at the periphery of the block as shown in FIG. 8C, for example, when the _edge ≦ bb_range, for example, the correction unit 110 regards the block noise as an edge. Do not judge.

  Moreover, the correction | amendment part 110 adjusts the adjustment signal corresponding to the block boundary determined to be block noise based on said determination result based on bb_range, for example, as shown in FIG. Here, the gain curve data shown in FIG. 9 is stored in, for example, a storage unit (not shown), a ROM, or the like, and is appropriately read out by the correction unit 110.

  For example, the correction unit 110 adjusts the degree of correction indicated by the adjustment signal as described above, and corrects the scaled image signal based on the adjusted adjustment signal, thereby realizing local correction processing. Needless to say, the local correction processing in the image processing apparatus 100 according to the embodiment of the present invention is not limited to the above.

  In addition, when performing the local correction process, the correction unit 110 has, for example, a dedicated configuration having an arbitrary configuration for performing the local correction process as described above in addition to the configuration related to the correction of the image signal such as a multiplier. However, the configuration of the correction unit 110 is not limited to the above. For example, in the image processing apparatus 100 according to the embodiment of the present invention, a control unit (not shown) may serve as the correction unit 110, and the correction unit 110 is a general-purpose processing circuit that can perform other processing. It may be configured.

  For example, with the configuration shown in FIG. 1, the image processing apparatus 100 (A) detects block noise based on an input image signal, outputs noise information, and (B) performs scaling processing on the input image signal. A process of outputting scaling information, (C) a process of outputting an adjustment signal based on noise information and scaling information, and (D) a process of correcting the scaled image signal based on the adjustment signal. Here, by performing the processes (A) to (D), it is possible to generate an adjustment signal based on the noise information and the scaling information, and to correct the scaled image signal based on the adjustment signal. The That is, the processes (A) to (D) correspond to the processes related to the image processing method according to the embodiment of the present invention described above. Therefore, the image processing apparatus 100 can execute the image processing method according to the embodiment of the present invention described above, for example, with the configuration shown in FIG.

  Therefore, the image processing apparatus 100 can achieve high image quality when scaling processing is performed on a compression-encoded image signal.

  Note that the configuration of the image processing apparatus 100 according to the embodiment of the present invention is not limited to the configuration shown in FIG. For example, FIG. 1 illustrates a configuration in which the image processing apparatus 100 includes the noise reduction unit 104, but the image processing apparatus 100 according to the embodiment of the present invention may have a configuration that does not include the noise reduction unit 104. It is. Even with the above configuration, the image processing apparatus 100 according to the embodiment of the present invention can correct the scaled image signal based on the adjustment signal generated based on the noise information and the scaling information. Noise is prevented from being emphasized. Therefore, it is possible to prevent deterioration in image quality due to emphasis on block noise that may occur when the conventional technique is used. Therefore, higher image quality can be achieved than when the conventional technique is used.

  As described above, the image processing apparatus 100 according to the embodiment of the present invention is based on the noise information indicating the block noise detected based on the input image signal and the scaling information indicating the enlargement ratio or the reduction ratio in the scaling process. The adjustment signal is generated, and the scaling image signal is corrected based on the adjustment signal. Here, even if other processing such as scaling is performed between the noise detection unit that detects block noise and the correction unit that performs image processing for improving image quality, the image processing apparatus 100 Image processing is performed in consideration of the effect of the above processing. Therefore, in the image processing apparatus 100, for example, even if linear scaling or non-linear scaling is performed on the input image signal, block noise is not enhanced by image processing (correction processing). That is, the image processing apparatus 100 can realize more natural image processing even for an image in which block noise has occurred.

  Therefore, the image processing apparatus 100 can achieve high image quality when scaling processing is performed on a compression-encoded image signal.

  As described above, the image processing apparatus 100 has been described as an embodiment of the present invention. However, the embodiment of the present invention is not limited to such an embodiment. Embodiments of the present invention include, for example, computers such as PCs (Personal Computers) and PDAs (Personal Digital Assistants), display devices such as television receivers, portable communication devices such as mobile phones, video / music playback devices (or video). / Music recording / playback apparatus), game machines, and the like, which can be applied to various devices capable of processing image signals.

(Program according to an embodiment of the present invention)
A program for causing a computer to function as the image processing apparatus according to the embodiment of the present invention (for example, a program for realizing the processes (A) to (D) above). When a scaling process is performed on a compression-encoded image signal by a program for realizing a process related to the processing method, a high image quality can be achieved.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, FIG. 1 shows a configuration in which the image processing apparatus 100 generates an adjustment signal based on noise information and scaling information, but the image processing apparatus according to the embodiment of the present invention is not limited to the above. For example, when the image processing apparatus according to the embodiment of the present invention performs other processing in which the position of the block noise detected between the noise detection unit and the correction unit is changed, the image processing apparatus according to the embodiment of the present invention. The image processing apparatus may be configured to generate an adjustment signal using noise information and information related to the other process (or using noise information, scaling information, and information related to the other process). Is possible. Even with the above configuration, it is possible to prevent block noise from being emphasized by image processing (correction processing). Therefore, in the case where scaling processing is performed on a compression-coded image signal, High image quality can be achieved.

  In the above description, it has been shown that a program (computer program) for causing a computer to function as the image processing apparatus according to the embodiment of the present invention is provided. However, the embodiment of the present invention further includes the above program. Recording media stored respectively can also be provided.

  The configuration described above shows an example of the embodiment of the present invention, and naturally belongs to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 100 Image processing apparatus 102 Noise detection part 104 Noise reduction part 106 Scaling part 108 Adjustment signal production | generation part 110 Correction | amendment part 112, 112A, 112B Noise measurement part 114 Filter part 116 Minimum value determination part 118 Adjustment signal output part 120 Adjustment part

Claims (9)

A noise detector that detects block noise based on the compression-encoded input image signal and outputs noise information indicating the detected block noise;
A scaling unit that performs scaling processing for enlarging or reducing the image indicated by the input image signal to the input image signal, and outputs scaling information indicating the enlargement rate or reduction rate;
An adjustment signal generating unit that outputs an adjustment signal indicating the degree of correction based on the noise information and the scaling information;
Based on the adjustment signal, a correction unit that corrects the image signal subjected to the scaling process;
An image processing apparatus comprising: The adjustment signal generator is
Based on the noise information and the scaling information, a noise measurement unit that specifies the distance from the block boundary of the block noise in the enlarged or reduced image,
An adjustment signal output unit that outputs the adjustment signal corresponding to the identified distance from the block boundary;
The image processing apparatus according to claim 1, comprising:   The image processing apparatus according to claim 2, wherein the noise measurement unit specifies a distance from the block boundary in the horizontal direction and / or a distance from the block boundary in the vertical direction.   The image according to claim 2, wherein the adjustment signal generation unit further includes an adjustment unit that adjusts a degree of correction indicated by the adjustment signal based on information indicating the intensity of the block noise included in the noise information. Processing equipment. The correction unit is
Local block noise is determined based on the image signal on which the scaling processing has been performed, and the degree of correction indicated by the adjustment signal is adjusted according to the determination result;
The image processing apparatus according to claim 1, wherein the image signal on which the scaling processing has been performed is corrected based on an adjustment signal whose degree of correction has been adjusted. The adjustment signal generation unit outputs an adjustment signal for adjusting the gain of the image signal,
The image processing apparatus according to claim 1, wherein the correction unit adjusts a gain of the image signal on which the scaling processing has been performed based on the adjustment signal. It further includes a noise reduction unit that reduces block noise of the input image signal,
The image processing apparatus according to claim 1, wherein the scaling unit performs the scaling process on an input image signal in which block noise is reduced. Detecting block noise based on the compression-encoded input image signal, and outputting noise information indicating the detected block noise;
Performing a scaling process for enlarging or reducing the image indicated by the input image signal on the input image signal, and outputting scaling information indicating an enlargement ratio or a reduction ratio;
Outputting an adjustment signal indicating a degree of correction based on the noise information and the scaling information;
Correcting the image signal on which the scaling processing has been performed based on the adjustment signal;
An image processing method. Detecting block noise based on the compression-encoded input image signal, and outputting noise information indicating the detected block noise;
Performing a scaling process for enlarging or reducing the image indicated by the input image signal on the input image signal, and outputting scaling information indicating an enlargement ratio or a reduction ratio;
Outputting an adjustment signal indicating a degree of correction based on the noise information and the scaling information;
Correcting the scaled image signal based on the adjustment signal;
A program that causes a computer to execute.

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